Hi,
I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Would it give more protection / solve the problem, if I encased it
in a fibreglass yacht mast which I happen to have ?

I plan it to be approx 40' high with the top 25' being a fibreglass
yacht mast with the wire running up the inside. Top would be
insulated / sealed so no ions could spray out, attracting a strike
.... am I going the right way ?

Thanks,
Nick

I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Hi Nick,
There is virtually nothing you can do to prevent a strike hitting your
antenna. But you can attempt to pursuade Mother Nature to send the damaging
electrons somewhere where they won't do damage. Get a Polyphaser or ICE or
other good lightning arrestor made for this purpose and install it with a good
ground under the antenna. Your objective is to divert the strike around your
equipment and into the ground, taking the path that YOU provide for, not the
one that the lightning strike would otherwise select. Your ground must have
the capacity to absorb the electrons which arrive in massive quantities in a
few microseconds, otherwise they will give up on you and find their own path
to ground, often not the way you would prefer.
There is good information on this technique on the polyphaser website,
probably www.polyphaser.com. Most likely you will get about 50 more replies
so be prepared, this is one of the favorite and most often discussed topics on
this newsgroup.

Rick K2XT

"Nick" wrote in message
...
Hi,
I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Would it give more protection / solve the problem, if I encased it in a
fibreglass yacht mast which I happen to have ?

I plan it to be approx 40' high with the top 25' being a fibreglass yacht
mast with the wire running up the inside. Top would be insulated / sealed
so no ions could spray out, attracting a strike ... am I going the right
way ?

Thanks,
Nick
Nick

With the voltages involved in a lightning strike, the fibreglass mast will
not make much, if any, difference. Rain fall and dirt deposits will create a
conductive path along the mast a few days or weeks after it has been
erected. Lightning is attracted to the highest pointiest thing in an area,
no matter what substance it is made from. Churches and trees are made of
insulating materials and they attract more strikes than anything else on
land. It was common to have to regularly rebuild the towers and steeples of
medieval churches before lightning conductors were installed. The average
steeple usually lasting no more than a century before suffering catastrophic
damage from a lightning strike. At the time, this was just accepted as a
sign that the parishioners were insufficiently pious, or had transgressed in
some way.

The fibreglass mast is ideal as a support and to provide weather protection
for your antenna element(s), but do not count on it reducing the chances of
a lightning strike it it is the tallest structure within 400 yards or so.
Various tables and maps are available on the internet showing the frequency
of lightning strikes per year per square mile or square kilometer for most
areas in earth. These should help you evaluate the risks in your particular
area. Forty feet is not particularly high and if you live in an area with
less than 20 lightning days per year, I would evaluate the risk of a strike
as being low. There is always a statistical risk and that's a chance you
have to accept when dealing with any force of nature.

Try to ensure that there is a good earth connection at the base of the
vertical antenna using earth rods and/or buried radial wires so that in
event of a strike, the lightning energy is dissipated into the ground rather
than transmitted along the feedines into your house. A switch to disconnect
and earth the antennas when equipment is not in use is always a good idea. A
look through the MFJ catalogue will give you an idea of what equipment is
available.

Mike G0ULI

On Mon, 12 Nov 2007 14:33:10 GMT, "Nick" wrote:

Would it give more protection / solve the problem, if I encased it
in a fibreglass yacht mast which I happen to have ?

Hi Nick,

No, it wouldn't.

Make the antenna shorter, and surround it with taller, nearby grounded
vertical conductors for the lightning to select in preference. For
more protection, connect the tops of the taller conductors over the
antenna.

Of course, this advice reduces to putting the antenna in a grounded
cage that takes the hit. Unfortunately it also renders the antenna
deaf.

Moral: Trying to stop the lightning from hitting your antenna also
stops RF.

[Hint: if you are going to stop it with a super glom of insulation,
like fiberglass, consider that this insulation is inferior to a
bajillion miles of air already there surrounding the antenna. That
doesn't slow down lightning much does it?]

73's
Richard Clark, KB7QHC

Rick wrote:
I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Hi Nick,
There is virtually nothing you can do to prevent a strike hitting your
antenna. But you can attempt to pursuade Mother Nature to send the damaging
electrons somewhere where they won't do damage. Get a Polyphaser or ICE or
other good lightning arrestor made for this purpose and install it with a good
ground under the antenna. Your objective is to divert the strike around your
equipment and into the ground, taking the path that YOU provide for, not the
one that the lightning strike would otherwise select. Your ground must have
the capacity to absorb the electrons which arrive in massive quantities in a
few microseconds, otherwise they will give up on you and find their own path
to ground, often not the way you would prefer.
There is good information on this technique on the polyphaser website,
probably www.polyphaser.com. Most likely you will get about 50 more replies
so be prepared, this is one of the favorite and most often discussed topics on
this newsgroup.

Rick K2XT



-----------


I agree with Rick.

Additionally, don't forget that your homeowner's insurance policy will
usually reimburse you for damage incurred via lightning strikes. But be
sure to see it in writing. Personal assurances from your agent are not
enough. Have the agent show it in the writing of YOUR policy, or one
identical to the one that you will be purchasing.

The last thing that you need after the damage is done is for the
insurance company to try to wiggle out of covering your lightning
damaged equipment.

Ed, NM2K

Rick wrote:
I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Hi Nick,
There is virtually nothing you can do to prevent a strike hitting your
antenna. But you can attempt to pursuade Mother Nature to send the damaging
electrons somewhere where they won't do damage. Get a Polyphaser or ICE or
other good lightning arrestor made for this purpose and install it with a good
ground under the antenna. Your objective is to divert the strike around your
equipment and into the ground, taking the path that YOU provide for, not the
one that the lightning strike would otherwise select. Your ground must have
the capacity to absorb the electrons which arrive in massive quantities in a
few microseconds, otherwise they will give up on you and find their own path
to ground, often not the way you would prefer.
There is good information on this technique on the polyphaser website,
probably www.polyphaser.com. Most likely you will get about 50 more replies
so be prepared, this is one of the favorite and most often discussed topics on
this newsgroup.

Rick K2XT



-----------


I agree with Rick.

Additionally, don't forget that your homeowner's insurance policy will
usually reimburse you for damage incurred via lightning strikes. But be
sure to see it in writing. Personal assurances from your agent are not
enough. Have the agent show it in the writing of YOUR policy, or one
identical to the one that you will be purchasing.

The last thing that you need after the damage is done is for the
insurance company to try to wiggle out of covering your lightning
damaged equipment.

Ed, NM2K

On Mon, 12 Nov 2007 10:55:25 -0500, Ed Cregger
wrote:

The last thing that you need after the damage is done is for the
insurance company to try to wiggle out of covering your lightning
damaged equipment.

The first question they will investigate:
"Does your grounding meet code?"

73's
Richard Clark, KB7QHC

On Mon, 12 Nov 2007 14:33:10 GMT, "Nick" wrote:

Hi,
I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Would it give more protection / solve the problem, if I encased it
in a fibreglass yacht mast which I happen to have ?

I plan it to be approx 40' high with the top 25' being a fibreglass
yacht mast with the wire running up the inside. Top would be
insulated / sealed so no ions could spray out, attracting a strike
... am I going the right way ?

Thanks,
Nick

The popular solution seems to be the Alpha-Delta grounding antenna
switches. Unfortunately, There does not seem to be one that can be
operated remotely.

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

"Rick" wrote in message
...

I want to install a vertical, fed with an SGC230 at the bottom, but
concerned about minimising chance of a lightning strike on a bare
conductor.

Hi Nick,
There is virtually nothing you can do to prevent a strike hitting your
antenna.

Interesting topic!

I have a tall metal pole supporting one end of a long wire HF antenna. This
tall metal pole is set in 1 cu yard of concrete. Is this concrete suitable
for conduction into mother earth or should I run a large copper strap from
the pole to an earth rod?

JERD
VK5JE

Is this concrete suitable for conduction into mother earth or should I run
a large copper strap from the pole to an earth rod?

Hi Jerd,
The latter, and you should have more than one if possible. The strap should
not have bends in it, should be low inductance (a copper strap is better
than a wire, etc.). Remember there are zillions of electrons coming down
that pole, and they all have to get into the earth, and all the ones in
front are being pushed by the ones in back, all screaming "Hurry up, or get
the hell outta the way, cause I gotta go...... real bad." And if they don't
get outta the way, the ones in back will jump around them like a New York
driver in a traffic jamb, to find a faster way to get where they are headed.
And you don't want that to happen because the other path may be through your
coax and into your house/equipment.
Now how does that portray the situation? That's the best I can do !

Rick K2XT